By the unique design of the present invention, a reversible airfoil is realized. Lift can be accomplished on either side of the invention aircraft wing-type airfoil by an arrangement of bars movable through spaces in a rigid spar, each end of the bars connecting to a flexible slat that is covered by a flexible, movable skin. Joining several sets of the rigid spars and attending components will form an airfoil of sufficient size to be utilized as a sail on a sailboat. When a plurality of the invention airfoils are scaled accordingly and mounted vertically on a rigid stationary frame, a power generator can be obtained.